U.S. patent number 10,310,066 [Application Number 14/985,554] was granted by the patent office on 2019-06-04 for indirect passive radar detection method and system.
This patent grant is currently assigned to SAZE TECHNOLOGIES, LLC. The grantee listed for this patent is Jason Eicke, Max Scharrenbroich, Michael Zatman. Invention is credited to Jason Eicke, Max Scharrenbroich, Michael Zatman.
United States Patent |
10,310,066 |
Zatman , et al. |
June 4, 2019 |
Indirect passive radar detection method and system
Abstract
An indirect passive radar method and system utilizing
information obtained from a non-direct source and reflected signals
from an object to be identified to determine information associated
with the object to be identified, such as speed, location, shaped,
distance and so forth.
Inventors: |
Zatman; Michael (Silver Spring,
MD), Scharrenbroich; Max (Alexandria, VA), Eicke;
Jason (Herndon, VA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Zatman; Michael
Scharrenbroich; Max
Eicke; Jason |
Silver Spring
Alexandria
Herndon |
MD
VA
VA |
US
US
US |
|
|
Assignee: |
SAZE TECHNOLOGIES, LLC (Silver
Spring, MD)
|
Family
ID: |
66673282 |
Appl.
No.: |
14/985,554 |
Filed: |
December 31, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
62166384 |
May 26, 2015 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S
13/46 (20130101); G01S 13/003 (20130101) |
Current International
Class: |
G01S
3/46 (20060101); G01S 13/46 (20060101); G01S
13/00 (20060101) |
Field of
Search: |
;342/453 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Liu; Harry K
Attorney, Agent or Firm: Ascentage Patent Law, LLC Johnson;
Travis Lee
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Patent Provisional
Application No. 62/166,384 filed on May 26, 2015 herein
incorporated by reference in its entirety.
Claims
We claim:
1. An indirect passive radar method comprising the steps: providing
a receiver, having a passive radar processor operatively connected
thereto; receiving, at the receiver, a reflected signal from a
target object using a receiver at a receiving location that does
not have a direct over-the-air line of sight position with a
transmitter emitting an original signal transmission, the reflected
signal resulting from the original signal transmission being
emitted from the transmitter that is subsequently reflected from
the target object; accessing and obtaining reference signal
information about the original signal transmission from an
alternative means other than by a direct over-the-air transmission
or connection from the transmitter to the receiver; comparing the
reflected signal to the reference signal information; calculating,
utilizing the passive radar processor, at least one of the
following: a range, location, speed, shape or other property of the
target object based in part on the comparison of the reflected
signal to the reference signal information.
2. The method of claim 1, wherein the alternative means includes
utilizing any of the following: internet, cable tv feed, satellite
downlink.
3. The method of claim 1, wherein the target is stationary.
4. The method of claim 1, wherein the target is a moving
object.
5. The method of claim 4, wherein characteristics regarding the
target's motion are determined locally and wherein the location or
speed calculation is based in part on the target's motion.
6. The method of claim 1, wherein the receiver includes a plurality
of antennae.
7. The method of claim 1, further comprising receiving multiple
reflected signals from multiple targets.
8. The method of claim 7, further comprising receiving multiple
reference signals correlating to each of the multiple reflected
signals.
9. The method of claim 1, further comprising placing the receiver
on a movable platform.
10. The method of claim 1, wherein the reference signal information
is re-modulated to create a filter and the filter is used on the
received reflected signal.
11. The method of claim 1, wherein the alternative means includes a
database containing receive reference signal information relating
to the original signal transmission.
12. The method of claim 1, wherein the reference signal is
re-modulated prior to comparing the reference signal to the
received reflected signal.
13. The method of claim 1, wherein the steps are applied to any of
the following: all types of radar systems or radar-like systems
including: ground, sea/water, air or space-based, or ionosondes
that perform any of the following types of radar functionality
including: search, track, moving target indicator, imaging,
synthetic aperture, target identification, or weather radar.
14. An indirect passive radar system comprising: a receiver having
at least one antenna positioned only to receive a reflected
transmission, the reflected transmission having been originally
omitted in an original form from a third-party transmitter, wherein
the reflected transmission represents a variant of the original
form which has been reflected of off a target object thus forming
the reflected transmission; a transmission database containing
reference signal information relating to the original form of the
reflected transmission, the transmission database being provided
separately from the emitter and the receiver; a processing unit,
the processing unit being operatively connected to the receiver,
the processing unit being configured to receive, indirectly from
the third-party transmitter, information from the transmission
database and reference signal information relating to the original
form of the reflected transmission as contained in the transmission
database; and wherein the processing unit uses the transmission
database and reference signal information to generate a filter that
is applied to the reflected transmission from the target
object.
15. The indirect passive radar system of claim 14, wherein the
processing unit calculates one of the following: speed, direction
or shape of the target object by comparing the reflected
transmission and the reference signal information; and wherein the
processing unit sends the calculated information to an output
device.
16. An indirect passive radar method comprising the steps:
providing a receiver, having a passive radar processor operatively
connected thereto; receiving, at the receiver, a reflected signal
being reflected off a target object using a receiver at a receiving
location, an original signal transmission being emitted from a
transmitter, reflected off the target, thus resulting in the
reflected signal; accessing a transmission database containing
reference signal information relating to the original form of the
reflected signal, the transmission database being provided
separately from the emitter and the receiver; obtaining reference
signal information from the transmission database, the reference
signal information being obtained indirectly from the third-party
transmitter, the reference signal information comprising
information regarding the original form of the reflected signal;
comparing the reflected signal to the reference signal information;
calculating, utilizing the passive radar processor, at least one of
the following: a range, location, speed, shape or other property of
the target based in part on the comparison of the reflected signal
to the reference signal information.
Description
COPYRIGHT INFORMATION
A portion of the disclosure of this patent document contains
material that is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or the patent disclosure, as it appears in the
Patent and Trademark Office patent file or records, but otherwise
reserves all copyright rights whatsoever.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present embodiments relate generally to Passive Radar Systems
and Methods.
2. Description of the Prior Art
Active radar systems are generally comprised of a transmitter and
receiver, each connected to an antenna. A signal is sent by the
transmitter and received by the receiver where the measured time
delay for the signal to travel to the object and back is converted
into a distance and the measured frequency shift due to the Doppler
effect is converted into a relative velocity.
In contrast, passive radar systems exploit the presence of
third-party transmitters, such as radio transmitters, television
transmitters, other radar transmitters and so forth, instead of
using their own transmitter. Conventional passive radar systems
require the use of multiple receivers and antennas. The first
receiver--herewith denoted as a reference receiver--is connected to
an antenna which is directed towards each third-party transmitter
or group of transmitters in order to receive high quality copies of
the transmitted signals. An additional receiver--herein denoted as
the target receiver--is connected to an antenna directed towards
the target(s). A passive radar system is able to detect the
presence of targets by comparing the signals received from the
reference and target receivers and measuring the time and frequency
differences between the direct path signals from the third-party
transmitter and the signal from the third-party transmitter that
is/are reflected off of the target. This allows the bi-static range
and bi-static Doppler shift of the target to be determined (see
FIG. 1).
In some embodiments, multiple third-party transmitters are used by
the passive radar and multiple reflected signals are received by
one or more receivers to detect targets and determine their
distance, shape, speed and location (see FIG. 2).
This results in two significant limitations for conventional
passive radar systems. First is the requirement for both target and
reference receivers. The second is that a passive radar's reference
receivers must be able to obtain a high-quality copy of the third
party transmitter(s') signals, thus limiting the siting and
coverage of passive radar systems, both in terms of distance from
the third party transmitters and the topography or interfering
objects that lie between the transmitters and the reference
receivers. The proposed application seeks to address these and
other limitations of current passive radar systems.
SUMMARY OF THE INVENTION
Disclosed is a system and method for an indirect passive radar
system which does not require the use of reference receivers for
obtaining copies of the third-party transmitter's signal. The
information contained within the third-party transmitter's signal
is obtained through an alternative means such as through the
internet, cable feed, satellite downlink or other source. After
obtaining the signal information, the signal information is used to
form an ideal copy of the third-party transmitter's signal (a
process herein referred to as re-modulation). The ideal copy of the
third-party's transmitter signal is compared with the signal
observed on the target receiver to detect the target and measure
the time and frequency differences between the re-modulated signals
from the third-party transmitter and the signal from the
third-party transmitter that is reflected off of the target. This
allows the bi-static range and bi-static Doppler shift of the
object to be determined.
In some embodiments, multiple third-party transmitters are used by
the indirect passive radar system by obtaining the information
contained within the signals through the internet, cable feed,
satellite downlink or other source, and multiple reflected signals
are received by one or more receivers in order to detect targets
and determine their distance, shape, speed and location.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a schematic showing bi-static range
geometry;
FIG. 2 illustrates a schematic utilizing a conventional or direct
passive radar system that can determine location information of a
target from third-party transmitters that are directly viewable
over the air by a receiver;
FIG. 3 is an example of a schematic using an indirect passive radar
system in accordance with various aspects of the present invention
having a passive receiver and a mobile target;
FIG. 4 is another example of a schematic using an indirect passive
radar system in accordance with various aspects of the present
invention having a passive receiver, a mobile target and stationary
target;
FIG. 5 is an example of using an indirect passive radar system in
accordance with various aspects of the present invention where a
passive receiver receives reflected signals from multiple
third-party sources reflecting from the same mobile target;
FIG. 6 is a flowchart illustrating a method of using an indirect
passive radar system; and
FIG. 7 is an indirect passive radar system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Aspects and embodiments relate generally to the field of
determining object or target information using indirect passive
radar systems and methods where information related to the signal
content of the third-party transmitter can be obtained from a
non-direct source such as through the internet, cable feed,
satellite communication or the like.
Conventional passive radar systems have a passive radar processor
that processes the signal received by the reference receiver to
form a filter which is then applied to the signal received from the
target receiver in order to detect the presence of a target. The
filter formed by the passive radar processor is typically a matched
filter, or a matched filter derivative that is optimized to remove
interference such as other signals in the environment or
ground-clutter.
Passive radar systems typically obtain their location from a map,
the Global Positioning System (GPS), or some other geolocation
technique. Once their position is known they use a database to
determine which local third party transmitters should be used.
FIG. 1 illustrates a basic bi-static radar geometry schematic that
shows the transmitter and receiver being separated by a distance
and using geometry to determine the location of the target or
object. Bi-static radar equations and geometry have been developed
since the 1930's.
FIG. 2 illustrates a basic schematic of a conventional passive
radar system, showing multiple third-party transmitters that have
their respective signals reflected off the target or object (an
airplane as shown) being received by the target receiver while the
reference receivers collect the third-party transmitter signals
directly. The passive radar processor then compares the reference
receiver signals with the target receiver signals to detect the
target and determine speed, location, direction, shape and the
like.
FIG. 3 illustrates a basic schematic of an indirect passive radar
system, where the receiver 34 does not have a direct over-the-air
line of sight with the third-party transmitter 10. A transmitted
signal 20 is emitted from the third-party transmitter 10, which is
reflected off a mobile target 50 as reflected signal 40. Reflected
signal 40 is then received by the passive receiver 34. The passive
receiver shown in these figures are shown mounted on a military
ship, but could be placed on or be a part of any building, vehicle,
backpack, or other indirect passive system that is mobile or
stationary. The indirect radar processor unit connected to the
passive receiver also receives reference information contained in
the third-parties' transmitter signals through a non-direct source
60 such as the internet, cable television feed or satellite
downlink, and the like. The indirect passive radar processor unit
then re-modulates the third-party reference signal content received
from the non-direct source 60 into the format of the third party
transmitter signal (20,40) and compares the re-modulated signal
with the reflected signal 40 to detect a target and determine its
determine speed, location, direction, shape and the like.
The Indirect Passive Radar Processor is used to generate one or
more filters from the information in the third party's reference
signal content received by the non-direct source 60 which are
applied to the signal received by the passive receiver 34 in order
to detect the presence of a target 50. The Indirect Passive Radar
Processor applies an extra step of processing when compared to a
conventional Passive Radar Processor. The information about the
third party's transmitted signal obtained through the internet,
cable television feed, satellite downlink or other source will be
at a different frequency and may have a different format compared
to the signal 20 transmitted over the air that illuminates the
target 50. Thus, the Indirect Passive Radar Processor must take the
reference signal information obtained from the non-direct source
60, (the internet, cable television feed, satellite downlink or
other source) re-modulate it to the format used in the over-the-air
transmission 20 and shift to an appropriate frequency prior to
forming and applying the filter(s) to the signal 40 received by the
passive receiver 34 in order to detect the presence of a target 50
and determine speed, location, direction, shape and the like.
Public sources such as tvfool.com and antennapoint.com along with
many other database sources, provide physical locations of public
transmitters, frequencies, and other detailed information that can
used to determine the physical location of the third-party
transmitters, channels, networks, call signs, and frequency they
are transmitting at to aid with determining where to find the
reference signal content. Once that is identified a filter can be
generated to identify the specific received over-the-air
transmitted signal from the specific third-party transmitter 10
with its location. For example, if the indirect passive radar
system has access to a cable feed for a local Boston NBC TV
broadcast, the system can utilize public sources to identify the
location and frequency of the local NBC TV broadcast signal;
re-modulate the NBC signal content to be used as a filter for the
over-the-air NBC transmitted signal and use this filtered signal to
detect moving targets, such as airplanes, and determine their
direction, speed, location, shape, and so forth using the bi-static
radar and Doppler effect equations.
FIG. 4 illustrates a similar schematic to that of FIG. 3, but
includes receiving a reflected signal from a stationary object 54.
Reference signal information is still received from a third-party.
The indirect passive radar system can be utilized to identify both
moving and non-moving targets as shown in FIG. 4.
FIG. 5 illustrates a similar schematic to FIG. 3, with the
utilization of additional third-party transmitters. A second
third-party transmitter 14 is shown emitting an over-the-air signal
24 that is reflected from the target 50, wherein the reflected
signal 44 is received by the receiver 34. An additional filter can
be generated from receiving reference signal information from the
non-direct source 60, re-modulating that signal to create the
filter to utilize the over-the-air signals emanating from 14 as
well as 10. In some embodiments a single antenna 34 can accomplish
this, while in other embodiments a second receiver antenna 34 can
be employed. The additional information can help further refine
information regarding the target 50 including speed, direction,
shape, and so forth. The filter formed by the indirect passive
radar processor may be a matched filter, or a matched filter
derivative that is optimized to remove interference, such as other
signals in the environment or ground-clutter.
FIG. 6 illustrates a flow chart illustrating a method 600 of using
an indirect passive radar system as described herein. As mentioned,
utilization of databases 602, which include information regarding
local transmitters' location, network affiliate, frequency,
channel, call sign, strength, and so forth can be obtained from
public databases. Once a transmitter information is identified the
user can then identify a corresponding non-direct source 604 to use
to receive a reference signal 606. The user can receive the
reference signal 606 from the non-direct source 604. The indirect
radar processor can then be used to generate a filter 608 from the
reference signal 606 and transmitter database 602 by re-modulating
the reference signal 606. The user can point or direct a target
receiver 610 at a target to receive a reflected signal 612 from the
third-party over-the-air transmission. The over-the-air reflected
signal that is illuminating the target is detected 612 by applying
the filter(s) 608 and the bi-static range and Doppler of the target
estimated. This information can be compared 614 with the 3rd party
transmitter's location by means of the bistatic range and Doppler
equations to determine the target's position, shape, speed,
location and so forth. The indirect radar processor can then
display and/or otherwise report the results 616.
FIG. 7 illustrates a basic schematic of an indirect passive radar
system 700 that includes a processor 708 that is connected to or
receives information from a transmitter database 702, which
provides third-party transmitter information as described above.
The processor 708 also receives reference signal information from a
non-direct reference signal source 60, wherein said reference
information is used to create a filter for receiving the
corresponding over-the-air transmission signal that is received by
a receiver 34 that relays the over-the-air transmission information
to the processor unit 708. The processor unit can then output the
target information to a display or other output device 714, such as
a monitor, speaker, and so forth.
The information about the third party's transmitted signal obtained
through the internet, cable feed, such as television, satellite
downlink or other source will usually be at a different frequency
and can have a different format to the signal transmitted over the
air that illuminates the target. Thus, the Indirect Passive Radar
Processor must take the signal information obtained through the
internet, cable television feed, satellite downlink or other
source, re-modulate it to the format used in the over-the-air
transmission and shift to an appropriate frequency prior to forming
the filter and applying the filter to the signal received from the
target receiver in order to detect the presence of a target and
determine speed, location, direction, shape and the like.
By comparing the transmitted signal with the reflected over-the-air
transmission being received from the target object the time delay
may be used to determine the relative bi-static range between the
transmitter, target and receiver and the frequency shift may be
used to determine a relative velocity between the target and the
point of receipt. In such a case, if the locations and velocities
of the receivers and transmitters are known, the position and
velocity of the target can then be determined.
A database may be used to determine the transmitter locations for
the over-the-air signals and which transmissions should be used.
This signal origin location can be utilized in determining the
position, speed, and direction of the target based upon the
measured time delays and Doppler shifts. It will be appreciated
that the time delays and Doppler shifts from multiple transmitters
may be used. By increasing the number of signals and corresponding
points of origin for which this calculation is performed, the
direction and velocity may be estimated with better accuracy.
It will be appreciated that the Doppler equation for calculating
relative speed of an object is: F.sub.O=F.sub.S/(1-V.sub.s/C)
Where, F.sub.O is the observed frequency, F.sub.S is the emitted
frequency, C is the velocity of the original transmission medium,
i.e. radio waves, V.sub.s is the relative velocity of the target
with respect to the transmitter and receiver.
The above description is merely illustrative. Having thus described
several aspects of at least one embodiment of this invention
including the preferred embodiments, it is to be appreciated that
various alterations, modifications, application to different types
of radar system and improvements will readily occur to those
skilled in the art. Such alterations, modifications, application to
different types of radar system and improvements are intended to be
part of this disclosure, and are intended to be within the spirit
and scope of the invention. It will be further appreciated that any
of the above described features and principles can be applied in
any number of suitable combinations and configurations.
Accordingly, the foregoing description and drawings are by way of
illustration and example only.
* * * * *